State of the art air purifiers use different techniques for removing gas pollutants from air. For example, activated carbon adsorption, thermal catalytic oxidation (TCO), chemisorption, plasma oxidation, photocatalytic oxidation (PCO), are commonly used gas abatement techniques.
A problem related to these techniques is that their efficiency depends on particular parameters of the air, such as humidity, temperature, etc. For example, the activated carbon adsorption technique is not efficient when the relative humidity (RH) of air is higher than 70%. The efficiency of the chemisorption technique is very low when the RH of air is below 30%. Thermal catalytic oxidation, more specifically, low cost TCO material such as MnOx-based metal oxide materials, show high activity of formaldehyde abatement at room temperature under low RH (<30%). However, under high RH, the material shows deactivation/poisoning due to the through strong adsorption on the active sites, especially at low temperatures.
DE 10 2014 103609 A1 describes an air filtering system which uses an air quality parameter to adapt its functionality. DE 10 2014 103609 A1 does not discuss the issue of filtering efficiency at changing RH levels of air in a room.
US 2014/0216259 A1 describes an air purifier including a humidifation filter. When humidity is low, the amount of air generated by air blowers inside the device is increased. When humidity is high, the amount of air generated by the air blowers inside the device is decreased. US 2014/0216259 A1 does not discuss the issue of filtering efficiency at changing RH levels of air in a room.
As indoor humidity is variable, there is a need for a highly efficient air purifying device, capable of working at a wide range of air humidity levels.